Cobalt-based cladding alloy for engine valve and engine

ABSTRACT

A cobalt-based cladding alloy for an engine valve includes, by mass %: Cr: 13% to 35%; Mo: 5% to 30%; Si: 0.1% to 3.0%; C: 0.04% or less; Ni: 15% or less; W: 9% or less; Fe: 30% or less; Mn: 3% or less; S: 0.4% or less; and Co and inevitable impurity elements as a remainder. The amount of Co is 30% or more.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-175665 filed onSep. 8, 2016 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a cobalt-based cladding alloy for anengine valve, and an engine provided with an engine valve on which acladding material made of the cobalt-based cladding alloy is deposited.

2. Description of Related Art

A cobalt-based cladding alloy excellent in corrosion resistance and wearresistance is employed by a valve face of an engine valve.

For example, Japanese Patent Application Publication No. 5-84592 (JP5-84592 A) discloses a cobalt-based cladding alloy consisting of, byparts by weight, Cr: 10% to 40%, Mo: more than 10% to 30%, W: 1% to 20%,Si: 0.5% to 5%, C: 0.05% to 3%, Al: 0.001% to 0.12%, 0: 0.001% to 0.1%,Fe: 30% or less, Ni: 20% or less, Mn: 3% or less, and Co and inevitableimpurity elements as the remainder (here, the amount of Co is 30 wt % to70 wt %).

SUMMARY

According to the cobalt-based cladding alloy described in JP 5-84592 A,since Fe is contained in an amount of 30% or less, the toughness isimproved, oxides are formed, and the effect as a lubricant is exhibited.Cr, Mo, and W contained therein causes solid solution strengthening ofthe Co-rich matrix, and by regulating the O content by adding Al, thecladding properties can be improved. In addition, since the valve faceof the engine valve operated under a high load is cladded, the wearresistance of the engine valve is improved, and the low attackability issimultaneously achieved, thereby achieving a cobalt-based cladding alloyexcellent in cladding properties.

However, for the purpose of reducing an environmental impact load,ethanol, ethanol-blended gasoline, compressed natural gas (CNG),liquefied petroleum gas (LPG) and the like are applied as the fuelengine. A vehicle using ethanol and ethanol-blended gasoline as the fuelis called a flexible-fuel vehicle (FFV).

When the ethanol-blended gasoline and the like are used, it is possibleto reduce the environmental impact load. However, a severe corrosiveenvironment or adhesive environment is formed compared to gasoline ofthe related art, and thus there is concern of excessive wear on a valveseat. Therefore, even with an engine provided with an engine valvehaving the cobalt-based cladding alloy described in JP 5-84592 A, thathas excellent performance, it is difficult for the engine to exhibithigh corrosion resistance and adhesion resistance compared to the caseof using ethanol-blended gasoline and the like.

The present disclosure provides a cobalt-based cladding alloy for anengine valve capable of exhibiting high corrosion resistance andadhesion resistance even in a case where ethanol-blended gasoline or thelike is used, and an engine provided with an engine valve on which acladding material made of the cobalt-based cladding alloy is deposited.

According to a first aspect of the present disclosure, a cobalt-basedcladding alloy for an engine valve includes, by mass %: Cr: 13% to 35%;Mo: 5% to 30%; Si: 0.1% to 3.0%; C: 0.04% or less; Ni: 15% or less; W:9% or less; Fe: 30% or less; Mn: 3% or less; S: 0.4% or less; and Co andinevitable impurity elements as a remainder (here, the amount of Co is30% or more).

While the amount of C in the cobalt-based cladding alloy described in JP5-84592 A is 0.05 mass % to 3 mass %, the amount of C in thecobalt-based cladding alloy for an engine valve according to the aspectof the present disclosure is 0.04 mass % or less. In this respect, thetwo sides are significantly different from each other.

That is, since the amount of C in the cobalt-based cladding alloydescribed in JP 5-84592 A is 0.05 mass % or more, hard carbide phasesare likely to be generated, and as the amount of the carbide phasesincreases, there is a concern that the attackability may increase. Anexcessive increase in the attackability of the clad metal affects anincrease in wear of the opponent valve seat.

In addition, due to the generation of the carbides, the amount of solidsolutions of Cr and Mo decreases, and there is a concern that theadhesion resistance or corrosion resistance may decrease.

Contrary to this, since the amount of C in the cobalt-based claddingalloy according to the aspect of the present disclosure is 0.04 mass %or less, the attackability can be reduced, and thus it becomes possibleto suppress wear of the opponent valve seat.

In addition, since the amount of C is small, the generation of carbidesis suppressed, and thus a reduction in the amount of solid solutions ofCr and Mo is suppressed, resulting in a cobalt-based cladding alloyprovided with high corrosion resistance and adhesion resistance.

As described above, the difference in the amount of C is extremelyimportant, and in a case where the above-mentioned ethanol-blendedgasoline or the like is used, the difference in effect due to thedifference in the amount of C becomes more significant.

According to a second aspect of the present disclosure, an engineincludes: an engine valve on which a cladding material made of thecobalt-based cladding alloy is deposited. A fuel for the engine is anyone of ethanol, ethanol-blended gasoline, compressed natural gas (CNG),and liquefied petroleum gas (LPG).

Since the engine according to the second aspect of the presentdisclosure is provided with the engine valve on which the claddingmaterial made of the cobalt-based cladding alloy in which the amount ofC is set to 0.04 mass % or less is deposited, wear of the opponent valveseat of the engine valve is suppressed, resulting in an engine havinghigh durability.

As can be understood from the above description, according to thecobalt-based cladding alloy for an engine valve according to the secondaspect of the present disclosure, since the amount of C is set to 0.04mass % or less, the attackability is reduced, and the generation of hardcarbides is suppressed. Therefore, a cobalt-based cladding alloyprovided with high corrosion resistance and adhesion resistance can beobtained, and wear of the opponent valve seat can be suppressed.

In addition, it is possible to provide an engine that is highly durableeven in a severe corrosive environment or adhesive environment due tothe use of ethanol, ethanol-blended gasoline, CNG, LPG, or the like as afuel.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a longitudinal sectional view of an engine valve having a cladportion made of a cobalt-based cladding alloy according to an embodimentof the present disclosure;

FIG. 2 is a view showing the results of a wear test, and is a viewparticularly showing the relationship between the total wear amount ofthe engine valve and a valve seat and the amount of C in thecobalt-based cladding alloy;

FIG. 3 is an enlarged view of a range in which the amount of C is 0 mass% to 0.05 mass % in FIG. 2; and

FIG. 4 is an SEM image of an example and a reference example before andafter a corrosion test.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a cobalt-based cladding alloy for anengine valve according to an embodiment of the present disclosure willbe described with reference to the drawings.

Embodiment of Cobalt-Based Cladding Alloy for Engine Valve

FIG. 1 is a longitudinal sectional view of an engine valve having a cladportion made of the cobalt-based cladding alloy according to theembodiment of the present disclosure. As illustrated in the figure, aclad portion 20 made of the cobalt-based cladding alloy is annularlyformed on the valve face of an engine valve 10, and a valve seat (notillustrated) is disposed on the opponent side on which the clad portion20 abuts at a high pressure when the engine valve 10 is mounted on acylinder head.

Here, the cobalt-based cladding alloy consists of, by mass %: Cr: 13% to35%; Mo: 5% to 30%; Si: 0.1% to 3.0%; C: 0.04% or less; Ni: 15% or less;W: 9% or less; Fe: 30% or less; Mn: 3% or less; S: 0.4% or less; and Coand inevitable impurity elements as the remainder (here, the amount ofCo is 30% or more).

Since an appropriate amount of Mo is added to the alloy that forms a Crpassive film, regeneration of the Cr passive film can be promoted.Therefore, even when the Cr passive film is broken due to corrosion orsliding of the clad portion 20, the speed of the regeneration of the Crpassive film by Cr and Mo exceeds the speed of the breakage, resultingin a cobalt-based cladding alloy having high corrosion resistance andadhesion resistance even in a repeatedly sliding and highly corrosiveenvironment.

The reasons for the numerical range of each metal element will bedescribed below in detail.

Cr: 13 Mass % to 35 Mass %

When Cr is in an amount of less than 13 mass %, a passive oxide film isnot formed and corrosion resistance is not exhibited. Therefore, thelower limit of the amount of Cr is defined as 13 mass %. When the amountof Cr exceeds 35 mass %, the cladding properties deteriorate. Therefore,the upper limit of the amount of Cr is defined as 35 mass %.

Mo: 5 Mass % to 30 Mass %

When the amount of Mo is less than 5% by mass, the effect of improvingthe corrosion resistance is insufficient. Therefore, the lower limit ofthe amount of Mo is defined as 5 mass %. When the amount of Mo exceeds30 mass %, the cladding properties deteriorate. Therefore, the upperlimit of the amount of Mo is defined as 30 mass %.

Si: 0.1 Mass % to 3.0 Mass %

When the amount of Si is less than 0.1 mass %, the cladding properties(wettability) deteriorate. Therefore, the lower limit of the amount ofSi is defined as 0.1 mass %. When the amount of Si exceeds 3.0 mass %,the attackability increases. Therefore, the upper limit of the amount ofSi is defined as 3.0 mass %.

C: 0.04 Mass % or Less

When the amount of C exceeds 0.04 mass %, the corrosion resistancedecreases and a eutectic structure having low corrosion resistance isformed, resulting in corrosion. Therefore, the attackability against thevalve seat increases. In addition, the amount of solid solutions of Crand Mo decreases, resulting in a decrease in the corrosion resistance.Therefore, the upper limit of the amount of C is defined as 0.04 mass %.

Ni: 15 Mass % or Less

Ni is an element that contributes to the improvement in the toughnessand corrosion resistance of the clad metal. When the amount of Niexceeds 15 mass %, the wear resistance decreases, and the claddingproperties deteriorate. Therefore, the upper limit of the amount of Niis defined as 15 mass %.

W: 9 Mass % or Less

W is an element that contributes to the improvement in the wearresistance of the clad metal. When the amount of W exceeds 9 mass %, themelting point rises and the cladding properties deteriorates due to therise of the melting point. Therefore, the upper limit of the amount of Wis defined as 9 mass %.

Fe: 30 Mass % or Less

Fe is an element that contributes to the improvement in the toughness ofthe clad metal. When the amount of Fe exceeds 30 mass %, the corrosionresistance decreases. Therefore, upper limit of the amount of Fe isdefined as 30 mass %.

Mn: 3 Mass % or Less

Mn is an element that contributes to the improvement in the claddingproperties. When the amount of Mn exceeds 3 mass %, the wear resistancedecreases. Therefore, the upper limit of the amount of Mn is defined as3 mass %.

S: 0.4 Mass % or Less

S is an element that contributes to the improvement in the claddingproperties (wettability) and a property that promotes discharge ofblowholes. When the amount of S exceeds 0.4 mass %, solidificationcracking occurs. Therefore, the upper limit of the amount of S isdefined as 0.4 mass %.

While the amount of C in the cobalt-based cladding alloy described in JP5-84592 A as above is 0.05 mass % to 3 mass %, the amount of C in thecobalt-based cladding alloy for an engine valve according to theembodiment of the present disclosure is 0.04 mass % or less.

Since the amount of C in the cobalt-based cladding alloy described in JP5-84592 A is 0.05 mass % or more, hard carbide phases are likely to begenerated, and as the amount of the carbide phases increases, theattackability tends to increase. An excessive increase in theattackability of the clad metal affects an increase in wear of theopponent valve seat. In addition, due to the generation of the carbides,the amount of solid solutions of Cr and Mo decreases, and the adhesionresistance or corrosion resistance tends to decrease.

Contrary to this, since the amount of C in the cobalt-based claddingalloy according to the embodiment of the present disclosure is 0.04 mass% or less, the attackability can be reduced, and thus it becomespossible to suppress wear of the opponent valve seat. In addition, sincethe amount of C is small, the generation of carbides is suppressed, andthus a reduction in the amount of solid solutions of Cr and Mo issuppressed, resulting in a cobalt-based cladding alloy provided withhigh corrosion resistance and adhesion resistance.

As an engine provided with the engine valve 10 having the clad portion20, an engine to that any one of ethanol, ethanol-blended gasoline, CNG,and LPG is applied as the fuel for the engine is exemplified.

Since the engine is provided with the engine valve 10 having the cladportion 20 on which the cladding material made of the cobalt-basedcladding alloy in which the amount of C is set to 0.04 mass % or less isdeposited, wear of the opponent valve seat of the engine valve 10 issuppressed even in a severe corrosive environment or adhesiveenvironment, and thus the engine has high durability.

Experiments and Results Verifying Corrosion Resistance of Engine Valve,Wear Resistance of Engine Valve and Valve Seat, and the Like

The present inventors conducted experiments to verify the corrosionresistance of the engine valve, the wear resistance of the engine valveand the valve seat, and clad beads. Table 1 below shows the compositionof each of the cobalt-based cladding alloys (Examples 1 to 11) accordingto the embodiment of the present disclosure and cladding alloys ofComparative Examples 1 to 19. Table 2 shows the experimental resultsregarding the corrosion resistance, wear resistance, clad beads, andactual machine wear of each of the cobalt-based cladding alloys. Inaddition, regarding the results of a wear test, particularly therelationship between the total wear amount of the engine valve and thevalve seat and the amount of C in the cobalt-based cladding alloy isshown in Tables 3-1 and 3-2 below and FIGS. 2 and 3, and an SEM image ofan example and a reference example before and after a corrosion test isshown in FIG. 4. Here, Reference Examples 1 and 2 in Tables 3-1 and 3-2refer to the cobalt-based cladding alloy disclosed in JP 5-84592 Adescribed above. In addition, the opponent valve seat of the enginevalve is a Fe-based valve seat, and is Fe-16Mo-21Co-2.4Mn-1.1C (by mass%).

First, in an experiment regarding the corrosion resistance of the enginevalve, a test surface (mirror-polished surface) of a specimen havingplanar dimensions of 20 mm×20 mm and a height of 2 mm was immersed in anetchant at a pH of 2.0 for 24 hours, and the cross section of the testsurface was observed with SEM to check the presence or absence ofcorrosion on the outermost layer of the test surface.

In an experiment regarding the wear resistance, the valve face of theengine valve is clad by a plasma cladding method (output 130 A,processing speed 8 mm/sec), a single body wear test was conducted, andby using an axial wear amount of 170 μm as a threshold, a wear amount of170 μm or more was evaluated as impossible (X) in Tables 2 and 3-2.

Here, the summary of the single body wear test will be described. Thistest is a test to investigate the attackability and wear resistance ofthe cladding material. Specifically, a sliding portion between a valveface that was clad and a valve seat made of a Cu-based material and aFe-based sintered material was subjected to a propane gas combustionatmosphere using a propane gas burner as a heating source. The wear testwas conducted for 8 hours by controlling the temperature of the valveseat to 200° C., applying a load of 176 N when the valve face and thevalve seat were brought into contact with each other by a spring, andbringing the valve face and the valve seat into contact with each otherat a rate of 2000 times/min. In this wear test, the depressed amount ofthe valve from a reference position was measured. The depressed amountof the valve corresponds to the wear amount (wear depth) to that theengine valve and the valve seat were worn by contact.

In addition, in an experiment regarding the clad beads, it was verifiedwhether or not the cladding properties were poor and whether or notcladding can be performed on the valve face. In Tables 2, and 3-2, thoseon which cladding could be performed were evaluated as possible (O), andthose on which cladding could not be performed were evaluated asimpossible (X).

In addition, in an experiment regarding the actual machine wear, anactual machine durability test was conducted for 300 hours using a 2400cc gasoline engine and an alcohol-containing fuel, and in Tables 2 and3-2, the limit reference value of the wear amount (the total wear amountof the engine valve and the valve seat) is shown as 100.

TABLE 1 Chemical composition (mass %) Co Cr Mo Ni W Si C Fe Mn EXAMPLE 1Remainder 21 12 6 3 0.8 0.01 5 0.3 EXAMPLE 2 Remainder 21 12 0 3 0.80.01 5 0.3 EXAMPLE 3 Remainder 21 12 0 0 0.8 0.01 5 0.3 EXAMPLE 4Remainder 21 12 0 0 0.8 0.01 1 0.3 EXAMPLE 5 Remainder 13 5 0 0 0.8 0.011 0.3 EXAMPLE 6 Remainder 13 5 0 0 0.8 0.04 1 0.3 EXAMPLE 7 Remainder 215 0 0 0.8 0.01 1 0.3 EXAMPLE 8 Remainder 21 12 0 0 0.8 0.01 25 0.3EXAMPLE 9 Remainder 21 12 6 3 0.8 0.04 5 0.3 EXAMPLE 10 Remainder 21 126 3 3.0 0.01 5 0.3 EXAMPLE 11 Remainder 21 12 6 3 0.8 0.01 0 3.0COMPARATIVE EXAMPLE 1 Remainder 13 5 0 0 0.8 0.05 1 0.3 COMPARATIVEEXAMPLE 2 Remainder 21 12 6 3 0.8 0.05 5 0.3 COMPARATIVE EXAMPLE 3Remainder 21 12 6 3 0.8 1.00 5 0.3 COMPARATIVE EXAMPLE 4 Remainder 21 120 0 0.8 0.05 0 0.3 COMPARATIVE EXAMPLE 5 Remainder 35 30 15 0 0.8 0.05 00.3 COMPARATIVE EXAMPLE 6 Remainder 35 30 0 0 0.8 0.04 0 0.3 COMPARATIVEEXAMPLE 7 Remainder 35 32 0 0 0.8 0.04 0 0.3 COMPARATIVE EXAMPLE 8Remainder 21 12 6 10 0.8 0.01 0 0.3 COMPARATIVE EXAMPLE 9 Remainder 11 50 0 0.8 0.01 1 0.3 COMPARATIVE EXAMPLE 10 Remainder 21 0 0 0 0.8 0.01 00.3 COMPARATIVE EXAMPLE 11 Remainder 35 30 15 10 0.8 0.01 0 0.3COMPARATIVE EXAMPLE 12 Remainder 35 30 15 12 0.8 0.01 0 0.3 COMPARATIVEEXAMPLE 13 Remainder 21 12 0 0 0.8 0.01 30 0.3 COMPARATIVE EXAMPLE 14Remainder 21 12 6 3 0.1 0.01 0 0.3 COMPARATIVE EXAMPLE 15 Remainder 2112 6 3 3.5 0.01 0 0.3 COMPARATIVE EXAMPLE 16 Remainder 21 12 6 3 0.80.01 5 3.5 COMPARATIVE EXAMPLE 17 26 Remainder 27 — — 5 — 1.3 0.3(Stellite 6) COMPARATIVE EXAMPLE 18 27 — 21 — 3.8 — — 0.5 0.3 (SUH35)COMPARATIVE EXAMPLE 19 28 — — — — — — — 0.3 (SUH35 nitriding)

TABLE 2 Wear resistance Axial wear amount (μm) Corrosion Engine ValveTotal Clad Actual machine resistance Determination valve seat amountbeads wear EXAMPLE 1 ◯ ◯ 4 29 33 ◯ 62 EXAMPLE 2 ◯ ◯ 2 26 28 ◯ Notconducted EXAMPLE 3 ◯ ◯ 7 34 41 ◯ Not conducted EXAMPLE 4 ◯ ◯ 10 50 60 ◯Not conducted EXAMPLE 5 ◯ ◯ 42 72 114 ◯ Not conducted EXAMPLE 6 ◯ ◯ 3781 118 ◯ Not conducted EXAMPLE 7 ◯ ◯ 50 80 130 ◯ Not conducted EXAMPLE 8◯ ◯ 13 34 47 ◯ Not conducted EXAMPLE 9 ◯ ◯ 3 32 35 ◯ 97 EXAMPLE 10 ◯ ◯46 112 158 ◯ Not conducted EXAMPLE 11 ◯ ◯ 10 158 168 ◯ Not conductedCOMPARATIVE EXAMPLE 1 X ◯ 45 71 116 ◯ Not conducted COMPARATIVE EXAMPLE2 X ◯ 4 47 51 ◯ 100 or more COMPARATIVE EXAMPLE 3 X ◯ 2 55 57 ◯ 100 ormore COMPARATIVE EXAMPLE 4 X ◯ 5 45 50 ◯ Not conducted COMPARATIVEEXAMPLE 5 X ◯ Not conducted X Not conducted COMPARATIVE EXAMPLE 6 ◯ ◯Not conducted X Not conducted COMPARATIVE EXAMPLE 7 ◯ ◯ Not conducted XNot conducted COMPARATIVE EXAMPLE 8 ◯ ◯ Not conducted X Not conductedCOMPARATIVE EXAMPLE 9 X ◯ 40 66 104 ◯ Not conducted COMPARATIVE EXAMPLE10 X X 96 92 203 ◯ Not conducted COMPARATIVE EXAMPLE 11 ◯ ◯ Notconducted X COMPARATIVE EXAMPLE 12 Not Not Not conducted X conductedconducted COMPARATIVE EXAMPLE 13 X ◯ 20 23 43 ◯ Not conductedCOMPARATIVE EXAMPLE 14 Not Not Not conducted X Not conducted conductedconducted COMPARATIVE EXAMPLE 15 ◯ X 7 230 237 ◯ Not conductedCOMPARATIVE EXAMPLE 16 ◯ X 50 130 180 ◯ Not conducted COMPARATIVEEXAMPLE 17 X X 120 105 225 ◯ X (100 or more for (Stellite 6) a time of1/10) COMPARATIVE EXAMPLE 18 X X 130 111 241 — Not conducted (SUH35)COMPARATIVE EXAMPLE 19 X ◯ 2 41 43 — X (100 or more for (SUH35nitriding) a time of 1/10)

TABLE 3-1 Chemical composition (mass %) Co Cr Mo Ni W Si C Fe Mn EXAMPLE1 Remainder 21 12 6 3 0.8 0.01 5 0.3 EXAMPLE 12 Remainder 21 12 6 3 0.80.03 5 0.3 EXAMPLE 9 Remainder 21 12 6 3 0.8 0.04 5 0.3 REFERENCEEXAMPLE 1 Remainder 21 12 6 3 0.8 0.05 1 0.3 REFERENCE EXAMPLE 2Remainder 21 12 6 3 0.8 1.00 1 0.3 COMPARATIVE EXAMPLE 17 26 Remainder27 — — 5 — 1.3 0.3 (Stellite 6) COMPARATIVE EXAMPLE 19 28 — — — — — — —0.3 (SUH35 nitriding)

TABLE 3-2 Wear resistance Axial wear amount (μm) Corrosion Engine valveTotal Clad Actual machine resistance Determination valve seat amountbeads wear EXAMPLE 1 ◯ ◯ 4 29 33 ◯ 62 EXAMPLE 12 ◯ ◯ 9 38 47 ◯ 70EXAMPLE 9 ◯ ◯ 3 32 35 ◯ 97 REFERENCE EXAMPLE 1 X ◯ 6 37 43 ◯ 100 or moreREFERENCE EXAMPLE 2 X ◯ 3 30 33 ◯ 100 or more COMPARATIVE EXAMPLE 17 X X120 105 225 ◯ X 100 or more for (Stellite 6) a time of 1/10 COMPARATIVEEXAMPLE 19 X ◯ 2 41 43 ◯ X 100 or more for (SUH35 nitriding) a time of1/10

TABLE 4-1 Chemical composition (mass %) Co Cr Mo Ni W Si C Fe Mn SEXAMPLE 13 Remainder 21 12 6 3 0.8 0.01 5 0.3 0.1 EXAMPLE 14 Remainder21 12 6 3 0.8 0.01 5 0.3 0.4 COMPAR- Remainder 21 12 6 3 0.8 0.01 5 0.30.5 ATIVE EXAMPLE 20

TABLE 4-2 Wear resistance Axial wear amount (μm) Corrosion Engine ValveTotal Clad resistance Determination valve seat amount beads EXAMPLE 13 ◯◯ 12 43 55 ◯ EXAMPLE 14 ◯ ◯ 13 41 54 ◯ COMPARATIVE Not conducted X(solidification EXAMPLE 20 cracking)

From Table 2, it could be seen that all of Examples 1 to 11 areexcellent in corrosion resistance, wear resistance, and claddingproperties.

Regarding the actual machine wear, in any of Examples 1 and 9 as theexperimental objects, the limit reference value of the wear amount wasless than 100, and good results are shown.

In contrast, in each of the comparative examples, any of corrosionresistance, wear resistance, and cladding properties is not satisfied.In any of Comparative Examples 2 and 3 as the experimental objects ofthe actual machine wear experiment, the result of the limit referencevalue of the wear amount is 100 or more.

In addition, it can be seen from Tables 3-1 and 3-2 and FIGS. 2 and 3,while the result of the limit reference value of the wear amount is 100or more in any of Reference Examples 1 and 2 (the cobalt-based claddingalloy disclosed in JP 5-84592 A) in which the amount of C is 0.05 mass %or more, in any of Examples 1, 9, and 12 in which the amount of C is0.04 mass % or less, the limit reference value of the wear amount islower than 100 and good results are shown.

It can be seen from FIG. 4 that, in the SEM image before and after thecorrosion test, while hard phases are formed after the corrosion testand corrosion is confirmed in Reference Example 2, in Example 6, nocorrosion is observed before and after the corrosion test.

Furthermore, it can be seen from Tables 4-1 and 4-2 that while any ofExamples 13 and 14 in which the amount of C is 0.04 mass % or less andthe amount of S is 0.4 mass % or less is excellent in corrosionresistance, wear resistance, and cladding properties, in ComparativeExample 20 in which the amount of S is 0.5 mass % or more,solidification cracking occurs, and it is confirmed that there is aproblem in cladding properties.

While the embodiment of the present disclosure has been described indetail with reference to the drawings, the specific configurations arenot limited to the embodiment, and design changes and the like withoutdeparting from the gist of the present disclosure are also included inthe present disclosure.

What is claimed is:
 1. A cobalt-based cladding alloy for an engine valvecomprising, by mass %: Cr: 13% to 35%; Mo: 5% to 30%; Si: 0.1% to 3.0%;C: 0.04% or less; Ni: 15% or less; W: 9% or less; Fe: 30% or less; Mn:3% or less; S: 0.4% or less; and Co and inevitable impurity elements asa remainder, wherein an amount of Co is 30% or more.
 2. An enginecomprising: an engine valve on which a cladding material made of thecobalt-based cladding alloy according to claim 1 is deposited, wherein afuel for the engine is any one of ethanol, ethanol-blended gasoline,compressed natural gas, and liquefied petroleum gas.